Recoilless Rifle 57mm

57mm M18a1 Recoilless Rifle

Type Classification:

Cont OTCM 37119 dtd 1959. Use:

This cartridge is used in 57mm recoilless Rifles M18A1 and M18 and is intended primarily for screening and spotting.


WP Cartridge M308A1 includes a perforated cartridge case containing a plastic liner and a percussion primer. The propelling charge is loosely loaded into the plastic liner. The cartridge case is crimped to the projectile just behind the pre-engraved rotating band. A steel adapter forms the front end of the projectile. The burster is press-fitted into the adapter, and the fuze is threaded into the adapter. The projectile is filled with white phosphorous.


The primer ignites the propellant when struck by the weapon firing pin, and the burning propellant generates gases to propel the projectile through the barrel. Recoil is eliminated because the design of the cartridge case permits the controlled release of some gas pressure through apertures in the rifle breech-block. The rotating band engages the barrel rifling to spin the projectile for stability in flight. On impact, the fuze functions to detonate the burster tube. The burster ruptures the projectile and disperses the white phosphorous filler. White phosphorous ignites spontaneously on contact with air, emitting a dense white smoke.

Difference Between Models:

M308 uses a paper-lined cartridge case and Percussion Primer M46.

Tabulated Data:

Complete round:



Old -------------------------------- Gray with yellow band and yellow markings

New ------------------------------- Light green with black markings

Burster ----------------------------- M21, 0.19 oz tetryl

Components: Cartridge case:

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